CBSE Class 8 Science Exemplar Chapter 17: Stars and Solar System NCERT Solutions

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NCERT Solutions PDF Class 8 PDF

This chapter, 'Stars and Solar System,' delves into the fascinating celestial bodies that populate our universe. The NCERT Solutions for Class 8 Science Exemplar provide clear explanations and answers to questions related to stars, planets, and their apparent movements. Students will learn about the 'morning star,' the significance of the Pole Star's position, and the Earth's rotation. The solutions also explore the behavior of objects in different gravitational environments, such as on the Moon, and the orbital characteristics of planets. These solutions are designed to help students grasp fundamental concepts of astronomy and prepare effectively for their exams by offering detailed, step-by-step explanations.

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Quick info

BoardCBSE
ClassClass 8
SubjectScience Exemplar
Session2026
LanguageEnglish
TypeNCERT Solutions
ChapterChapter 17

Chapter summary

Chapter 17, 'Stars and Solar System,' focuses on basic astronomical concepts. The NCERT Solutions cover multiple-choice questions about identifying celestial objects like Venus (morning star), understanding the fixed position of the Pole Star, and the Earth's rotation direction. It also touches upon the effect of gravity on projectile motion on the Moon and planetary orbital periods. These solutions aim to clarify the fundamental principles of our solar system and beyond for Class 8 students.

Learning outcomes

  • Identify Venus as the 'morning star'.
  • Understand the significance of the Pole Star's position.
  • Explain the Earth's direction of rotation based on the Sun's apparent movement.
  • Describe the motion of a ball thrown on the Moon's surface.
  • Relate the orbital period of a planet to its distance from the Sun.

Topics covered

Paper topics

  • Stars
  • Solar System
  • Morning Star (Venus)
  • Pole Star
  • Earth's Rotation
  • Apparent Movement of Sun
  • Gravity on Moon
  • Orbital Periods of Planets
  • Celestial Bodies

Important topics

  • Understanding the 'Morning Star'
  • Significance of the Pole Star
  • Earth's Rotation and Apparent Solar Movement
  • Effect of Gravity on Celestial Bodies
  • Orbital Mechanics of Planets

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Questions and Solutions

Multiple Choice Questions

1. Morning star is the name given to

  1. pole star
  2. star Sirius
  3. planet Jupiter
  4. planet Venus
Solution: The correct option is (d) planet Venus. Venus is often called the 'morning star' because it is the brightest planet visible in the sky before sunrise, appearing in the eastern horizon.

Multiple Choice Questions

2. Which of the following figures correctly depicts the position of the Pole Star?

[Note: The original source included figures which are not reproducible here. The solution describes the correct position.]

Solution: The correct answer is (a). The Pole Star is located in the direction of the Earth's axis of rotation in the Northern Hemisphere. Therefore, it appears stationary in the sky, always indicating the North direction. The figure depicting the Pole Star directly above the Earth's axis would be the correct representation.

Multiple Choice Questions

3. The Sun appears to move from east to west around the Earth. This observation implies that the Earth rotates from:

  1. east to west
  2. west to east
  3. north to south
  4. west to north
Solution: The correct option is (b) west to east. The apparent movement of the Sun from east to west across the sky is a direct consequence of the Earth's rotation on its axis from west to east.

Multiple Choice Questions

4. If an astronaut standing on the surface of the Moon throws a ball upwards, the ball would:

  1. directly fall down from the point it is released.
  2. hang in space.
  3. go up and then come back to the surface of the Moon.
  4. keep going up, never to come back.
Solution: The correct option is (c) go up and then come back to the surface of the Moon. Although the Moon has much weaker gravity than Earth (about 1/6th), it still possesses gravitational force. This force will pull the ball back down after it reaches its highest point, causing it to return to the lunar surface.

Multiple Choice Questions

5. Suppose a new planet is discovered orbiting between Uranus and Neptune. Its time period of revolution around the Sun would likely be:

  1. less than that of Neptune.
  2. more than that of Neptune.
  3. equal to that of Neptune or Uranus.
  4. less than that of Uranus.
Solution: The correct option is (a) less than that of Neptune. According to Kepler's Third Law of Planetary Motion, the orbital period of a planet is directly related to the size of its orbit (semi-major axis). A planet located between Uranus and Neptune would have an orbit smaller than Neptune's, meaning it is closer to the Sun and would complete its revolution in a shorter time period.

Common mistakes

  • Confusing planets with stars.
  • Incorrectly identifying the 'morning star'.
  • Misunderstanding the direction of Earth's rotation.
  • Assuming gravity on the Moon is the same as on Earth.

Revision tips

  • Review the definitions of celestial bodies like stars and planets.
  • Memorize the characteristics of the Pole Star and its importance.
  • Understand the cause-and-effect relationship between Earth's rotation and the Sun's apparent movement.
  • Visualize the effect of different gravitational forces on object motion.
  • Practice identifying celestial objects based on their descriptions.

Practice MCQs

Q1. Which celestial body is commonly referred to as the 'morning star' and is visible in the eastern sky before sunrise?

Q2. The Pole Star is significant because it is located in the direction of:

Q3. If the Sun appears to move from east to west across the sky, what does this imply about the Earth's rotation?

Q4. When an astronaut throws a ball upwards on the Moon, what is the most likely outcome?

Q5. If a new planet were discovered orbiting between Uranus and Neptune, what would be its likely orbital time period compared to Neptune's?

Frequently asked questions

What is the 'morning star' mentioned in Chapter 17?

The 'morning star' is the name given to the planet Venus, which is exceptionally bright and visible in the eastern sky before sunrise.

Why is the Pole Star important in the context of Earth's rotation?

The Pole Star is important because it appears to be stationary in the sky, located almost directly above the Earth's North Pole. This makes it a reliable reference point for direction.

How does the Earth's rotation affect the apparent movement of the Sun?

The Earth rotates from west to east. This rotation causes the Sun, Moon, and stars to appear to move across the sky from east to west.

What is the difference in gravity between the Moon and the Earth?

The acceleration due to gravity on the Moon is significantly less than that on Earth, approximately one-sixth. This means objects weigh less and behave differently when thrown.

How does the position of a planet affect its time period of revolution around the Sun?

Planets closer to the Sun have shorter orbital paths and therefore complete their revolution in a shorter time period compared to planets farther away.

Are the solutions provided for Chapter 17 accurate?

Yes, these solutions are based on the NCERT curriculum and provide accurate explanations for the concepts covered in Chapter 17: Stars and Solar System.

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